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Pale Cyst Nematode

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LM Dandurand, University of Idaho

The pale cyst nematode (Globodera pallida, PCN) is a soil-dwelling roundworm that

feeds on the roots of high-value crops such as potatoes, tomatoes, and eggplants.

PCN is native to South America and was discovered in Idaho in 2006. This pest can

remain dormant and viable in soil for 30 years.

PCN are microscopic cyst-forming nematodes. When a mated female dies, her body

hardens and becomes a cyst that contains between 300 to 500 viable eggs. If PCN

populations are left unchecked, they can reduce crop yields by 20 to 70 percent.
What To Look For

When PCN is detected, it stops commerce in potatoes and nursery stock. It can

seriously harm our agricultural production, environment, and economy. Here's what

to look for:

Cysts

Dead females (cysts) can be found on the roots and potato tubers. They

can stay dormant for up to 30 years, while the eggs inside remain viable.

Field damage

Stunted plants with yellowing leaves, wilting, and eventually plant death.

PCN Photo Gallery

Tap any image to view larger size.


Show Info

Female Globodera pallida on a root. You can also see a brown cyst (dead female) on

the same root. 

Bonsak Hammeraas, NIBIO - The Norwegian Institute of Bioeconomy Research,

Bugwood.org

Potato plants in the field showing signs of Globodera pallida. 

Florida Division of Plant Industry, Florida Department of Agriculture and Consumer

Services, Bugwood.org

Sign of Globodera pallida on potato. 

Florida Division of Plant Industry, Florida Department of Agriculture and Consumer

Services, Bugwood.org

How To Prevent This Pest

PCN spreads when soil from an infested field is moved to a new location on farming

equipment, seed potatoes, or waste from potato grading operations. All farming

equipment used on infested land must be pressure washed to remove soil.

Equipment with difficult to reach areas, such as harvesters, may need to be steam

treated or fumigated to ensure it is nematode-free. Pressure washing and steam

treatments are coordinated through APHIS.

To prevent the spread of PCN:

Make sure all farm machinery, trucks, construction, and other equipment are

clean when going from field to field. Do not allow any equipment in your fields

unless it has been thoroughly cleaned. This is especially important when

renting land, as you may not have records of previous crop history.

Check the condition of trucks and other vehicles entering your operation. Find

out where they have been and what sanitation treatments they have had. Seed

potato shipments are a particular concern for PCN spread because trucks may

make more than one stop.

Do not spread waste from potato grading, processing, or storage operations on

farmland or place it in an area where it can be spread to farmlands.

Leave hedgerows, sod barriers, or sod strips between fields and along

highways.
Buy only certified seed that comes from fields tested and found to be PCN-free.

Plant a PCN-resistant variety (if available) in your noninfested fields at least

once every 4 years.

Plant cover crops as soon as possible when land is not in use because wind and

water erosion can spread PCN cysts.

Tell people in your operation about the seriousness of PCN and potato diseases.

Make sure they follow all precautions. Provide equipment needed to conduct

proper cleaning and disinfection procedures.

Segregate potatoes in storage by field.

Do not reuse previously used bags or containers for potato transport. Be sure

all commercial transport vehicles are free of soil.

Do not allow temporary help, custom applicators, or utility companies to bring

their vehicles onto your farmland without proper cleaning. Do not allow them to

bring any bags or containers with them to the field.

Do not use common headlands, farm roads, and public roads as turning areas.

Prohibit nonauthorized entry onto farmlands using “No Trespassing” signs.

Do not assume that nonregulated fields are free of PCN.

How It Is Treated

PCN-infested fields are treated with a chemical fumigant in late summer or early fall

and sometimes in early spring, depending on soil temperature. These treatments

continue until PCN is eradicated. APHIS monitors eradication progress.

Report Plant Pests and Diseases

Have you seen this pest or signs of pest damage? Immediately report your findings.

Find your State plant regulatory official

Find your State plant health director

Controlling Pale Cyst Nematodes

Current Status
APHIS has successfully contained PCN to an 8.5-mile radius area in southeast Idaho,

preventing its spread to other potato-producing areas in the United States.

Quarantine Information

The following documents describe changes to the PCN-regulated areas, including

field maps and an explanation of the changes by date.

January 11, 2023

April 20, 2022

November 29, 2021

November 22, 2021

July 13, 2021

January 28, 2021

January 10, 2020 (110.29 KB)

January 10, 2020 Map (598.48 KB)

To request copies of archived quarantine information documents, please email us at

aphisweb@usda.gov.

APHIS' Response

APHIS conducts a containment program for PCN directed toward eradication. The

PCN Program’s overarching goals are to prevent the spread of PCN, delimit the

infestation, eradicate the pest, and preserve domestic and foreign markets. States

also conduct annual PCN surveys. 

Potato Cyst Nematode National Survey Plan (April 2009)

Frequently Asked Questions

Program-Associated Field Survey and Laboratory Result Definitions

Term Definition
Baseline Survey

A full‐field survey at a sampling rate of 8,000 cc of

soil per acre (equivalent to approximately 20

pounds of soil per acre) used to determine the

presence or absence of PCN. The baseline survey

is conducted as soon as practicable upon

becoming regulated as an associated field when

the field is not eligible to receive the first

delimiting survey towards deregulation (eligibility

requires at least one host crop grown and

harvested from the field since the time of

exposure to soil from an infested field).

Delimiting (Delimitation)

Survey

A full‐field survey at a sampling rate of 8,000 cc of

soil per acre (equivalent to approximately 20

pounds of soil per acre) used to determine the

presence or absence of PCN. A series of two

negative delimiting surveys, each following

harvest of the next two host crops grown on the

field, is required to deregulate an associated field.

Follow-up Survey

A full‐field survey used to determine the presence

or absence of PCN in fields where laboratory

results are inconclusive for PCN, suspect for PCN

by morphological/morphometric analysis, or

suspect for PCN by molecular (DNA) analysis. The

deregulation requirement for fields deemed

inconclusive for PCN or suspect for PCN by

morphological/morphometric analysis is a

series of two follow-up surveys at the delimiting

survey rate, one of which must follow the next

host crop grown on the field. The deregulation

requirement for fields deemed suspect for PCN

by molecular (DNA) analysis is a negative

follow-up survey at the delimiting survey rate,

following each of the next two host crops grown

on the field.

Negative for PCN  No PCN cysts were found.
Positive for PCN (Infested)

The minimum threshold for declaring a field

positive for PCN (infested) is met by detecting a

minimum of two cysts from two samples that were

identified as Globodera sp. by

morphological/morphometric analysis, and at least

one of the cysts was viable and confirmed as

Globodera pallida (PCN) by molecular (DNA)

analysis.

Suspect for PCN by DNA

Analysis

A single cyst was identified as Globodera pallida

(PCN) by morphological/morphometric and

molecular (DNA) analysis; however, the minimum

threshold for declaring a field positive for PCN

(infested) was not met.

Suspect for PCN by

Morphological/Morphometric

Analysis

Cyst(s) from one or more samples were identified

as Globodera sp. by morphological/morphometric

analysis. No viable, DNA‐containing material was

found inside the cysts, so a definitive

identification as Globodera pallida could not be

made.

Inconclusive for PCN

Object(s) resembling Globodera sp. cysts were

found in a soil sample(s); however, a definitive

identification could not be made using either

morphological/morphometric analysis or

molecular (DNA) analysis. Some morphological

characteristics of Globodera sp. were present such

that PCN could not be ruled out.

Confirmations and Deregulatory Actions

Infested Field Confirmation Policy

Deregulation Protocols

Associated Field Deregulation

Infested Field Deregulation

Deregulation Protocol for Regulated Non-Agricultural Land (flowchart)

Deregulation Land No Longer in Host Crop Production (flowchart)

Changes to Regulated Areas (archived documents available upon request)

Removal of Regulated Areas in Idaho (June 6, 2022) 
Addition of Regulated Areas in Idaho (January 18, 2022)

Removal of Regulated Areas Idaho (January 11, 2022)

Removal of Regulated Areas in Idaho (August 13, 2021)

Addition and Removal of Regulated Areas in Idaho (March 19, 2021) 

Addition of Regulated Areas in Idaho (January 17, 2020)

Regulatory Information

Federal Register Notices

September 16, 2016 (188.88 KB), Update of Quarantined Areas

September 8, 2010 (52.37 KB), Notice of Changes to Quarantined Area 

July 10, 2009 (48.35 KB), Notice of Changes to Quarantined Area 

May 7, 2009 (50.49 KB), Notice of Changes to Quarantined Area 

April 29, 2009 (90.13 KB), Final Rule 

April 10, 2009 (50.49 KB), Update of Quarantined Areas 

September 11, 2008 (49.57 KB), Update of Quarantined Areas 

June 6, 2008 (52.11 KB), Update of Quarantined Areas 

September 12, 2007 (120.36 KB), Interim Rule and request for comments 

PCN Regulations

7 CFR 301.86

Information for Cooperators

Potato Cyst Nematode Guidelines - These guidelines outline the surveillance

and phytosanitary actions used to detect and manage PCN (updated May 7,

2014)

Clarification to the Definition of "Field"

Amendment to Facilitate Research and Field Trials

Self-Sanitation Tracking Form, available as .docx, .pdf, and .xls

Spread the Word

Potato Cyst Nematode National Survey Plan: “Looking” To Keep Potato Markets

Open (brochure, May 2015)

Pest Alert: Potato Cyst Nematodes (May 2015)

Program Updates
Program Review

Five-Year Review: Idaho Falls, ID (March 2012)

Program Updates

2023, Fourth Quarter

2023, Third Quarter

2023, Second Quarter

2023, First Quarter

2022, Fourth Quarter

2022, Third Quarter

2022, Second Quarter

2022, First Quarter

To request copies of archived program updates, please email us at

aphisweb@usda.gov.

Final Environmental Documents

View All Final Environmental Documents

Contact Us

Lynn Evans-Goldner

National Policy Manager

Email: lynn.evans-goldner@usda.gov

Phone: 301-851-2286